Burner control system



April13,1937. a E HAW 2,076,967

BURNER CONTROL SYSTEM Filed Jan. 6, 1936 2 Sheets-Sheet l Jaw/72 02 April 13, 1937. B. E. SHAW 2,076,967

- BURNER CONTROL SYSTEM Filed Jan. 6, 1936 2 Sheets-Sheet 2 Patented Apr. 13, 1937 UNITED STATE BURNER CONTROL SYSTEM Burton E. Shaw, Adel, Iowa, assignor to Penn Electric Switch Company, Des Moines, Iowa, a

corporation of Iowa Application January 6, 1936, Serial No. 57,774

' 11 Claims.

An object of my invention is to provide a burner control system including a controller of simple, durable and inexpensive construction, which can be operated on either line voltage or like.

A further object is to provide a controller which eliminates the usual relay for controlling the burner, ,such relay usually being provided for energizing the motor and ignition mechanism of the'burner in response to temperature changes affecting a room thermostat connected in the coil circuit of the relay.

Another object is to provide a burner switch operated to a closed position by a slow acting means for operating certain parts of the controller.

Figure 3 is a diagrammatical view somewhat similar to Figure 1 showing the parts in the po- 5 reduced voltage supplied by a transformer or the overrunning electro-responsive means, a safety switch being opened by.the electro-responsive" means, whereupon the circuit thereto is broken and the safety switch will remain open if combustion does not occur to cause a combustion responsive member to again close it.

Another object is to provide a latch associated with the safety switch for latching it in open position upon eithercombustion failure after it is established, or in the event that combustion is not established, the latch being manually releasable for resetting the controller for automatic operation after whatever trouble caused the latch to operate has been remedied.

both a burner switch and a safety switch, so associated with a combustion responsive means that the one controller takes the place of a relay, .a safety switch and a combustion switch usually provided as separate units, my construction eliminating complicated wiring and reducing the controller to a simple form.

A still further object is to provide a combustion responsive switch in which a switch arm is A further object is to provide an actuator for lug IU of the tube II, and its other end secured initially moved upon combustion occurring or failing, by a friction shoe movable across an edge of a switch arm, the friction shoe slipping relative to such edge after the arm has been moved slightly.

5 with these and other objects in view, my inventlon consists in the construction, arrangement and combination of the various parts of the device, whereby the objects contemplated are attained, as hereinafter more fully set forth, point- 50 ed out in my claims, and illustrated in the accompanying drawings, in which:

Figure 1 is a front elevation of a burner controller embodying my invention.

Figure 2 is a sectional view on the line 2-2 55 of Figure 1 showing the combustion responsive sition caused by closure of the room thermostat.

position. I

Figure 4 is a similar view illustrating a further position occurring upon the combustion responsive means responding to combustion establishment.

Figure .5 is a similar view showing the position of the parts when the room thermostat opens the circuit.

Figure 6 is a similar view showing the position of the parts caused by combustion failure and resulting in latching of the safety switch in open 15 Figure 7 is an electro diagrammatical view showing the controller connected in circuit with low voltage supplying the room thermostat circult; and

Figure 8 is a similarview showing an installation using line voltage for the room thermostat circuit.

On the accompanying drawings I have used the reference numeral iii to indicate a switch casing. Within the casing ill a supporting board l2, preferably of insulation, is provided on which the various elements of the controller are mounted.

A tube it extends rearwardly from the casing Ill and is adapter. for positioning in a stack or other part of a furnace, so that a bimetal element I6 carried thereby is responsive to combustion temperatures. The tfmetal element I6 is U-shaped having one end secured to a stationary to one end of an arm 20. The arm 20 extends longitudinally through the tube I4 "and terminates in a T-head 22, which I shall term a fric tion shoe, for purposes which will hereinafter become obvious. The arm 20 extends through a slot 24 of the back of the casing III, while the head 22 extends through a slot 26 of the board i2. Mounted on the board I2 is a safety switch SS and a burner switch BS. The safety switch comprises a pair of leaf spring arms 28 and 30, suitably mounted on a block of insulation 32extending from the board l2. The safety switch is provided with contacts 34. The friction shoe 22 is adapted to. frictionally engage the upper end of the leaf spring 30, whereby the first slight I movement of the bimetal element [6 magnified by the arm 20 will move the spring 30 from the position of Figure 1 to the position of Figure 4, upon combustion occurring. Stop pins 36 and 38 are provided for the leaf spring 30, whereby after the spring is moved from one pin to the other,and the friction shoe continues to move, it can do so without imparting further movement to the leaf spring, but upon return move- 5 ment of the friction shoe, the spring will be immediately moved.

For the leaf spring 28 I provide a latch 44 pivoted at 42. The leaf spring 30 is provided with a cam 44 for rendering the latch at times inoperative. The latch is provided with a tail. piece 46, which can be swung downwardly for manually unlaching the latch after it assumes the position of Figure 6.

The burner switch BS comprises a switch arm 48 having a yoke 50 receiving one end of a bimetal warp element 52. The other end of the warp element is anchored to a stationary projection 54 extending from the board H. The switch arm 48 is pivotally mounted by a leaf spring 56 anchored to a stationary block 58.

The burner switch is provided with contacts 60 and the switch arm 48 preferably has an armature portion 62 associated with a permanent magnet 64 to secure snap action of the switch. The switch arm is connected by a link 66 with the leaf spring 28 of the safety switch.

Adjacent the bimetal warp element 52 I provide a heater H comprising a resistance element suitably supported at its ends on supports 63. The heater H, upon being energized, radiates heat to the warp element 52, causing it to warp from the position of Figure 1 to the position of Figure 3.

In Figure 7 I illustrate a burner motor at M and a transformer, at T. The burner switch BS is connected in circuit with the motor M, the supply wires being shown at a and b, and the connecting wires at c, d and e. The primary of the transformer T is indicated at 10 and the secondary thereof at 12. The secondary is connected by a wire I to a room thermostat RT having contacts 14. These contacts are connected by .a wire a with the safety switch SS and the heater H in series. From the heater H a wire it returns to the secondary I2.

In Figure 8 I illustrate a similar circuit, except that the transformer T is omitted, thereby supplying full line voltage to the room thermostat. The thermostat and the heater H, of

course, are then designed for the necessary higher voltage instead of for the low voltage required in an installation as shown in Figure 7.

' Practical operation In the operation of my burner control system, when the room-thermostat is open and the stack has cooled down, the parts are in the position of Figures 1, 7 and 8. Upon the room thermostat calling for heat, the circuit can be traced through the following elements in Figures '7 and 8: f,

RT, 14, y, 34, H and h. This will cause the resistance element H to be heated, so that it will warp to the position of Figure 3, thus closing the burner switch BS to establish the burner circult a, c 60, d, M, e and b.

The safety switch contacts 34 open, which breaks the circuit to the heater H before the burner switch closes. The residual heat in the heater, however, .and that absorbed by the bi- 7 metal element 52 causes an overrunning, which results in the continued movement toward a closed position of the burner switch, even after the contacts 34 are separated. The relative proportions of the parts, of course, must be designed 7 to effect this within the time period between separation of the contacts 34 and reclosure thereof by combustion occurrence, as illustrated in Figure 4. f

Upon combustion being established, the friction shoe 22 moves from the right toward the left, thus closing the contacts 34, as in Figure 4. In this position the cam 44 engages the latch 40 as illustrated, so that subsequently the latch will not latch the contacts 34 open as will short- 137 be apparent.

Providing combustion is successfully established, the parts will remain in the position of Figure 4 until the room thermostat opens the circoil; in response to sufficient heat being supplied by the furnace to the room. 'I'hereupon the heater H will cool down, permitting the burner switch to open, as in Figure 5, thus deenergizing the burner and leaving the safety switch contacts engaged, although placing the spring 28 under tension.

Thereafter the stack will cool down, permitting the safety switch to move from the position of Figure 5 to the position of Figure 1, with the cam 44 holding the latch 40 up so that it does not catch on the upper end of the spring 2%, and the parts are then in position for the next operation caused by the room thermostat closing.

In Figure 4 combustion hasbeen established. If combustion now fails before the room thermostat opens, the bimetal 52 will remain in the position of Figure 4, as shown in Figure 3, but

the friction shoe 22 will return from the position in Figure 4 to the position of Figure 3. This re- -moves the cam 44 from engagement with the latch 40 so that the latch can drop to latched position. Opening of the safety switch contacts 34 has resulted due to combustion failure after it has been established, so that the circuit for the heater H is then opened by the contacts 34, and the heater will cool down, permitting the position of Figure 6 to be assumed with the safety switch contacts latched in open position. Thereafter the controller cannot function in response remedied and the controller reset.

The time period between the-position of Figure 3 and Figure 6, in case that combustion does not occur, is the inherent safety time period of the safety switch. If this period is set for a minute and a half, for instance, combustion must occur within that period in order to close the safety switch as in Figure 4, to cause the burner to operate properly. If combustion does not occur within that period, the residual heat in the heater H and the bimetal 52 will be lost to such an extent that the burner switch BS opens and the controller is locked out. i

The particular means I have provided for actuating the switch arm 30 effectively provides for movement of the switch arm upon initial opera tion of the bimetal element I6 from either cold or hot position, and slippage thereafter without not occurring. In this case the trouble must be any undesired binding or gripping of the parts relative to each other.

It is obvious also from the foregoing that numerous changes might be madein the construction, arrangement and operation of the parts, and it is my purpose to cover by my claims any modifications in structure or use of mechanical equivalents, which may reasonably come within the scope of my invention and of the claims.

I claim as my invention:

1. In a burner controller, a switch, a slow acting overrunning electro-responsive means for closing said switch. upon energization of said means, a safety switch operable to tie-energize said means, said safety switch being opened by energization of said means before closure of said first switch, and combustion-responsive means for closing said safety switch upon combustion occurring.

2. In a burner controller, a switch, a slow act- .ing overrunning electro-responsive means for closing said switch upon energization of said means, a safety switch operable to tie-energize said means, said safety switch being opened by energization of said means before closure of said first switch, and combustion responsive means for closing said safety switch upon combustion occurring, a latch for said safety switch to latch it in open position, said combustion responsive meanscoacting therewith to render said latch inoperative upon the return of said safety switch to open position prior to the return of said combustion responsive means to cold position.

3. In a burner controller, a switch, a slow acting overrunning electro-responsive means for closing said switch upon energization of said means, a safety switch operable to tie-energize said means, said safety switch being opened by energization of said means before closure of said first switch, combustion responsive means for closing said safety switch upon combustion occurring, a latch for said safety switch to latch it in open position, said combustion responsive means coacting therewith to render said latch operative upon return of said combustion responsive means to cold position prior to return of said first switch to open position.

4. In a burner controller, a switch, a slow acting overrunning electro-responsive means for closing said switch upon energization of said means, a safety switch operable to (lo-energize said means, said safety switch being opened by energization of said means before closure of said first switch, combustion responsive means for closing said safety switch upon combustion occurring, and. a latch for said safety switch to latch it in open position.

5. In a burner controller, a switch, a heat responsive element for closing said switch upon said heat responsive element being heated, an electric resistance element for heating said heat responsive element, a safety switch operable to tie-energize said resistance element, said safety switch being opened by energization of said resistance element before closure of said first switch, and combustion responsive means for closing said safety switch upon combustion occurring.

6. In a. burner controller, a switch, a heat r sponsive element for closing said switch upon said heat responsive element being heated, an electric resistance element for heating said heat responsive element, a safety switch operable to ole-energize said resistance element, said safety switch being opened by energization of said resistance element before closure of said first switch, combustion responsive means for closing switch being opened by energization of said resistance element before closure of said first switch, combustion responsive, means for closing said safety switch upon combustion occurring,

and a latch for said safety switch to latch it in open position, said combustion responsive means coacting therewith to render said latch operative upon return of said combustion responsive means to cold position prior to return of said first switch to open position.

8. In a burner controller, a switch, a heat responsive element for closing said switch upon said heat responsive element being heated, an electric resistance element for heating said heat responsive element, a safety switch operable to deenergize said resistance element, said safety switch being opened by energization of said resistance element before closure of said first switch, combustion responsive means for closing said safety switch upon combustion occurring, and a latch for said safety switch to latch it in open position.

9. In a burner controller, a switch, a bimetal warp element for closing said switch upon the warp element being heated, a resistance element for heating said warp element, a safety switch operable to tie-energize said resistance element and opened by said warp element upon the warp element being heated, combustion responsive means to close said safety switch before said warp element returnsto normal position provided combustion is established, a latch for said safety switch, said combustion responsive means co-operating with said latch to render it inoperative upon return of said first switch to open position prior to the return of said combustion responsive means to cold position and to render it operative upon the return of said combustion responsive means to cold position prior to return of said first switch to open position.

10. In a burner controller, a switch including a swingable switch arm, means for actuating said switch arm comprising a frictional shoe movable across an edge thereof and in the plane of movement of said edge, and temperature responsive means for moving said friction shoe.

11. In a burner controller, a switch includin a swingable switch arm, means for actuating said switch arm comprising a. frictional shoe movable across an edge thereof and in the plane of movement of said edge, an elongated arm having said friction shoe on one end thereof, and means connected with the other end of said arm to swing it in response to temperature changes.

BURTON E. SHAW. 

